1. Technical Field
The present invention relates to an indicating plate (dial) for a timepiece arranged on a front surface side of a solar battery (solar cell) housed in a timepiece, the solar cell capable of converting light energy to electric energy for utilization thereof.
2. Background Art
It is common practice to employ a solar cell as a power source for watches, desktop electronic calculators, portable radio sets, etc. This solar cell is generally constructed of, for example, amorphous silicon and converts light energy to electric energy. In view of this function, the solar cell must be arranged in a position upon which light is incident, i.e., a surface position such that the solar cell is directly visible from outside.
The solar cell is commonly used in an indicating plate structure for wristwatch, which is constructed so that, referring to FIGS. 23 and 24, four solar cells 132 which are fan-shaped in a plan view are arranged, with an insulating band 133 therebetween, on an upper surface of wristwatch module 131. Further, a translucent resin thin film layer 135 is laminated onto part or the entire surface of each of the solar cells 132, with transparent plate 134 of a transparent polycarbonate (polycarbonic ester) resin or acrylic resin interposed therebetween.
In this indicating plate structure for a solar watch, however, the solar cells 132 are generally brown or dark-blue, so that, for example, the solar cells disposed under the transparent plate are viewed through the transparent plate. Thus, the dial takes on the color of the solar cells. Further, the insulating band 133 is between neighboring solar cells 132, so that the insulating bands 133 appear as cross lines. Thus, not only is the design inclusive of color tone extremely restricted, but also the appearance is degraded to thereby lower the commercial value.
On the contrary, a watch was proposed in which, for example, an interference filter was disposed on a front side of a solar cell to thereby prevent direct viewing of the solar cell. However, problems were encountered such that the supply of light energy to the solar cell was hampered and such that the appearance quality as watch dial was poor.
For solving these problems, for example, Japanese Patent Publication No. 5(1993)-38464 disclosed a colored solar cell comprising a solar cell and a color diffusing layer composed of a color filter disposed on a front side of the solar cell and capable of transmitting light having a wavelength within a region contributing to power generation of the solar cell and a scattering layer disposed between the solar cell and the color filter, which scattering layer was capable of transmitting a portion of the light transmitted through the color filter and scattering the rest of the light in all directions.
A white diffusion plate was employed as this scattering layer, and it was suggested to use as the white diffusion plate, for example, an acrylic milk white plate, a half mirror coated with a matting clear lacquer, a glass having one side roughened by blasting or a white diffusion plate having a mirror formed of, for example, aluminum in a stripe or net pattern on a side opposite to plastic.
However, in this prior art, although the acrylic milk white plate is used as the scattering layer, a metal tone favored in an indicating plate of wristwatch and capable of imparting an appearance of superior quality can not be obtained. Further, burrs occur at the time of working, thereby necessitating deburring. Accordingly, the process is complicated and the cost is increased. With respect to the half mirror coated with a matting clear lacquer, half mirror treatment and coating are required to thereby complicate the process. Further, it is probable that, depending on coating operation, the film thickness becomes nonuniform to thereby cause a dispersion of transmission factor with the result that mottling occurs. Moreover, with respect to the glass having one side thereof roughened by blasting or the white diffusion plate having a mirror formed of, for example, aluminum in a stripe or net pattern on a side opposite to plastic, blasting and mirror treatment are required to thereby complicate the process. Furthermore, depending on these treatments, the problem is encountered such that the film thickness and irregularity degree become nonuniform to thereby invite a dispersion of transmission factor and a mottling. Still further, all the above materials have a problem such that the appearance quality thereof as a watch dial is poor.
At any rate, the interposition of the above scattering layer between the color filter and the solar cell unfavorably requires a complicated process and invites a dispersion of transmission factor leading to a deterioration of power generation performance and an occurrence of mottling. Further, a deterioration of appearance quality due to the property of material per se is invited.
Furthermore, although, with respect to the metallic indicating plate for use in the indicating plate structure of the conventional timepiece, a design diversification can be attained by, for example, its peculiar metal color. In addition, in this case, various models thereof with a high quality and high grade appearance have been proposed. However, the metallic indicating plate cannot be employed in the solar watch because the use of the metallic indicating plate intercepts light to thereby disenable the power generation by the solar cell. Therefore, it has been unfeasible to realize an appearance of superior quality peculiar to metal color and an extensive design variation on the solar watch.
The present invention has been made taking the above problems into account. Therefore, it is an object of the present invention to provide an indicating plate for a timepiece through which the insulating band cross lines and solar cell positioned under the indicating plate are not viewed. Furthermore, the indicating plate of the present invention can be provided with a metallic color peculiar to metal and enables the same design expression as attained by the conventional metallic indicating plate. Still further, according to the indicating plate of the present invention, a design variation inclusive of a tone (delicate hue) and pattern with superior-quality appearance are extensively increased and an excellent appearance quality is accomplished to thereby ensure an enhanced commercial value.
The present invention has been made with a view toward solving the above problems of the prior art and attaining the above object. Accordingly, the indicating plate for a timepiece according to the present invention is an indicating plate for a timepiece to be arranged on a front surface side of a solar cell housed in a timepiece,
the timepiece indicating plate comprising a resin substrate through which light can be transmitted and a metallic thin film layer coating formed on at least one side of the resin substrate by dry plating,
the timepiece indicating plate not only capable of preventing viewing of the solar cell from outside thereof through the timepiece indicating plate but also having a light transmission at least sufficient to cause the solar cell housed under the timepiece indicating plate to generate power.
In this construction, the metallic thin film layer coating prevents viewing therethrough of the solar cell and cross lines disposed under the timepiece indicating plate. Some light is transmitted through the metallic thin film layer coating, and the light transmission is so large as to contribute to the power generation of the solar cell. Thus, the function of the solar timepiece per se is not inhibited. Moreover, coloring can be made by the metallic color peculiar to metal possessed by the metallic thin film layer coating, thereby enabling extensively increasing a design variation.
In this construction, although the thickness of the metallic thin film layer coating can appropriately be set taking the light transmission, etc. into account, it is preferred that the metallic thin film layer coating have a thickness of 100 to 500 xc3x85. The reason is that the solar cell and other items disposed under the indicating plate are not viewed therethrough and that some light is transmitted to thereby exhibit a light transmission which is so large as to contribute to the power generation of the solar cell with the result that the function of the solar timepiece per se is not inhibited. Furthermore, even if the same metallic thin film layer coating is used, various metallic colors can be obtained and the light transmission can be varied by changing the thickness of the metallic thin film layer coating within the above range.
The metallic thin film layer coating may consist of a single metallic thin film layer, or may be a multilayer coating consisting of at least two metallic thin film layers. The use of the multilayer coating consisting of at least two metallic thin film layers enables developing a delicate metallic color which cannot be produced by the use of the single metallic thin film layer.
Further, it is preferred that the metallic thin film layer coating have a portion partially cut off by masking or etching. In this construction, various patterns can be formed to thereby enable increasing a design variation.
The metallic thin film layer coating can be composed of one metal selected from the group consisting of Au, Ag, Al, Cu, Co, Cr, Fe, In, Ni, Pd, Pt, Rh, Sn and Ti or an alloy of at least two metals selected from the above group. Also, the metallic thin film layer coating can consist of a film of any of a nitride, an oxide and a carbide of the above metal or alloy, or can consist of a composite of such items.
Still further, it is preferred that the resin substrate have at least one side thereof at least partially provided with an irregular pattern. This construction enables the same design expression as realized by the conventional indicating plate, extensively increases a design variation inclusive of a tone and pattern with superior-quality appearance and enables developing a delicate hue.
On the other hand, the resin substrate can be composed of a transparent resin or a colored resin. The material of the resin substrate is not particularly limited, and, for example, a polycarbonate resin, an acrylic resin, a polyacetal resin, an ABS resin, a polyethylene resin, a polypropylene resin, a polystyrene resin or a polyethylene terephthalate resin can be used. When the resin substrate is composed of a colored resin, a design variation inclusive of tone can be increased, for example, a texture improvement can be attained by the use of the resin having the same color as that of the metallic thin film layer coating.
Further, the resin substrate may be composed of a blend of different types of resins known as polymer alloy, for example, a polymer alloy consisting of a combination of at least two resins selected from among a polycarbonate resin, an acrylic resin, a polyacetal resin, an ABS resin, a polyethylene resin, a polypropylene resin, a polystyrene resin and a polyethylene terephthalate resin.
The use of the above polymer alloy enables improving the adherence to metallic thin film layer coating, surface treatability, moldability and hygroscopic property of the resin substrate.
It is preferred that the metallic thin film layer coating have its upper surface covered with a surface protective layer. For example, a color coating, a gradation coating or a laminate film can be used as the surface protective layer. The surface protective layer enables not only protecting the metallic thin film layer coating from oxidation, etc. but also effecting, for example, a tone change to thereby increase a design variation.
In particular, when the metallic thin film layer coating provided on the resin substrate is composed of Ag or Cu, the metallic thin film layer coating suffers from discoloration, rust, etc. unless a surface protective layer is present on the surface of the metallic thin film layer coating. Therefore, the formation of the surface protective layer is requisite.
This surface protective layer may be one prepared from a synthetic resin based paint or ink. This paint or ink can be based on an acrylic resin, a urethane resin, an alkyd resin, an epoxy resin or a mixture thereof.
Further, the surface protective layer may be composed of a synthetic resin film such as a polyethylene film or a polyester film.
Still further, the surface protective layer may be composed of a metal oxide coating film. This metal oxide coating film can be formed by, for example, the vacuum deposition of a metal oxide such as MgO, TiO2, SiO2, SiO, ZrO2 or Al2O3. The formation of the metal oxide coating film on the surface of the resin substrate can be accomplished by the use of not only the above vacuum deposition technique but also other dry plating techniqueisuch as the ion plating or the sputtering technique.
Still further, the surface protective layer can be composed of a chromated coating film comprising as obtained by treating the metallic thin film layer coating with a solution containing chromic acid and a chromic salt to thereby form a chromate coating on the plating. The resin substrate may be embossed to thereby provide surface protrusions constituting time characters or the like. Further, the upper surface of the timepiece indicating plate can be provided with marking by printing. Also, time character or other marking member can be bonded onto the upper surface of the timepiece indicating plate.
Furthermore, it is preferred that the timepiece indicating plate be fitted with means for mounting the timepiece indicating plate on a timepiece frame. The mounting means can be, for example, cuts provided at the periphery of the indicating plate, protrusions provided at the periphery of the indicating plate, holes provided at the periphery of the indicating plate or protrusions provided on the back of the indicating plate.
In all the above constructions, it is preferred that the light transmission of the timepiece indicating plate be in the range of 10 to 50% lest the capability of power generation of the solar cell disposed under the timepiece indicating plate be inhibited.
On the other hand, according to the present invention, there is provided a process for producing an indicating plate for a timepiece to be arranged on a front surface side of a solar cell housed in a timepiece, the timepiece indicating plate comprising a resin substrate through which light can be transmitted and a metallic thin film layer coating formed on at least one side of the resin substrate, which process comprises the steps of:
conducting an injection molding of a resin, followed by punching according to necessity, to prepare a resin substrate; and
forming a metallic thin film layer coating on at least one side of the resin substrate by dry plating.
In this process, the dry plating can be conducted by any of the vacuum deposition, ion plating and sputtering techniques. It is preferred that the thickness of the metallic thin film layer coating formed by the dry plating range from 100 to 500 xc3x85. The reason is that the solar cell and other items disposed under the indicating plate are not viewed therethrough and that some light is transmitted to thereby exhibit a light transmission which is so large as to contribute to the power generation of the solar cell with the result that the function of the solar timepiece per se is not inhibited. Furthermore, even if the same metallic thin film layer coating is used, various metallic colors can be obtained and the light transmission can be varied by changing the thickness of the metallic thin film layer coating within the above range.
The employment of the above dry plating, which is a physical method, enables easily executing the coating application to a resin being a nonconductor, especially, only one side thereof as compared with the wet plating or the like. Also, it enables carrying out a film formation while monitoring the film thickness so that precision control of film thickness and massproduction with high reproducibility can be realized.
It is preferred that the injection molding be performed with the use of a metal mold having an irregular pattern provided on its inner surface so that at least one side of the resin substrate is at least partially provided with the irregular pattern. This metal mold can be fabricated by the conventional electrical forming (known as xe2x80x9celectroformingxe2x80x9d) method. The pattern produced by this method is, for example, an electroformed radial pattern or electroformed sandy pattern. The thus constituted process enables the same design expression as realized by the conventional indicating plate, extensively increases a design variation inclusive of a tone and pattern with superior quality appearance and enables developing a delicate hue.
Furthermore, for increasing the adherence between the metallic thin film layer coating and the basis constituting resin substrate and for enhancing the appearance quality and weather resistance reliability of the metallic thin film layer coating, it is preferred that cleaning of the resin substrate on its surfaces be performed prior to the step of forming the metallic thin film layer coating.
This cleaning is preferably accomplished by cleaning with the use of, for example, a neutral detergent to thereby degrease the surface of the resin substrate or remove particles or dust or by the method known as ion bombardment (ion bombarding method) in which moisture and residual gas molecules such as CO2, CO and H2 are removed from the surface of the resin substrate by the impact of inert gas ions.
Also, the above cleaning is preferably performed by heating the resin substrate so that moisture and residual gas molecules are removed. This heating is preferably performed in a reduced pressure, still preferably, in a vacuum.
Still further, the above step of forming the metallic thin film layer coating preferably includes masking and etching conducted to form a metallic thin film layer having partially cut off portion. Specifically, use can be made of a method in which the metallic thin film coating is formed in multilayers as permitted from the viewpoint of transmitted light quantity, the multilayer coating is provided with a masking of, for example, a photoresist and an upperlayer metal is partially removed by etching. In addition, a method in which, contrarily, the masking is first provided, subsequently the metallic thin film layer coating is formed and thereafter the topmost metallic thin film layer is removed together with the masking material can be used.
As a result, a design variation can be increased by a combination of various colors, namely, a combination of the metallic color of the topmost metallic thin film layer, the metallic color of the underlying metallic thin film layer and, if the resin substrate is colored, the color thereof.
It is preferred that the process comprise the step of covering the upper surface of the metallic thin film layer coating with a surface protective layer. For example, a color coating, a gradation coating or a laminate film can be used as the surface protective layer. The covering with the surface protective layer enables not only protecting the metallic thin film layer coating from oxidation, etc. but also effecting, for example, a tone change to thereby increase a design variation.
In particular, when the metallic thin film layer coating provided on the resin substrate is composed of Ag or Cu, the metallic thin film layer coating suffers from discoloration, rust, etc. unless a surface protective layer is present on the surface of the metallic thin film layer coating. Therefore, the formation of the surface protective layer is requisite.
This surface protective layer may be prepared from a synthetic resin based paint or ink. This paint or ink can be based on an acrylic resin, a urethane resin, an alkyd resin, an epoxy resin or a mixture thereof.
Further, the surface protective layer may be composed of a synthetic-resin film such as a polyethylene film or a polyester film.
Still further, the surface protective layer may be composed of a metal oxide coating film. This metal oxide coating film can be formed by, for example, the vacuum deposition of a metal oxide such as MgO, TiO2, SiO2, SiO, ZrO2 or Al2O3. The formation of the metal oxide coating film on the surface of the resin substrate can be accomplished by the use of not only the above vacuum deposition techniques but also other dry plating technique such as the ion plating or the sputtering technique.
Still further, the surface protective layer can be composed of a chromated coating film as obtained by treating the metallic thin film layer coating with a solution containing chromic acid to thereby form a chromate coating on the plating.
The process may comprise the step of embossing the resin substrate so that surface protrusions constituting time characters or the like are provided, prior to the step of forming the metallic thin film layer coating.
Further, it is preferred that the process comprise the finishing step of providing the upper surface of the timepiece indicating plate with marking by printing or with a marking member such as a time character by bonding.
Furthermore, it is preferred that, in the injection molding, the timepiece indicating plate be fitted with means for mounting the timepiece indicating plate on a timepiece frame by monolithic molding. The mounting means can be, for example, cuts provided at the periphery of the indicating plate, protrusions provided at the periphery of the indicating plate, holes provided at the periphery of the indicating plate or protrusions provided on the back of the indicating plate.